1. Field of the Invention
The present invention is related to a thin film transistor (TFT) array substrate and a manufacturing method thereof, and more particularly, to a TFT array substrate and a manufacturing method thereof that is capable of solving the abnormal alignment problem.
2. Description of the Prior Art
Liquid crystal displays (LCD) are widely used in mobile device such as mobile phones and digital cameras, personal computers, notebook computers, and home appliance. A conventional LCD panel includes a TFT array substrate, a color filter substrate opposite to the TFT array substrate, and a liquid crystal (LC) layer sandwiched in between the TFT array substrate and the color filter substrate. It is well-known to those skilled in the art that an alignment layer is respectively formed on the surface of the TFT array substrate that facing the LC layer and on the surface of the color filter substrate that facing the LC layer. The alignment layers are formed to uniformly maintain an initial alignment of the LC layer so that the LC molecules in the LC layer are oriented to a specific and predetermined arrangement.
Please refer to FIG. 1, which is a schematic drawing illustrating a conventional TFT array substrate of a twisted nematic (TN) LCD. As shown in FIG. 1, the conventional TFT array substrate 100 includes a substrate 101 having scan lines 102, data lines 104, and storage electrode lines 106 formed thereon. The scan lines 102 and the data lines 104 define pixel regions 108. And the TFT array substrate 100 also includes switch devices 110 respectively positioned in each pixel region 108. Of course, those of ordinary skill in the art will recognize that after forming the abovementioned lines and switch devices 110, an alignment material layer (not shown) is formed to cover the TFT array substrate 100. Then the alignment material layer is rubbed by use of a rubbing roll to form uniform microgrooves on the surface of the alignment material layer. Accordingly an alignment layer having a plurality of uniform microgrooves is obtained. The formed microgrooves exhibit a particularly high surface anchoring energy and yield a strong alignment to the LC molecules, and thus the LC molecules in the LC layer are arranged in the predetermined direction.
Please still refer to FIG. 1. It is well-known to those skilled in the art that when rubbing the alignment material layer, the rubbing roll moves along an alignment direction 120. For example, the conventional TFT array substrate 100 of the TN LCD apparatus has an included angle of 45° between the alignment direction 120 and the scan lines 102 or the data lines 104. Subsequent to the rubbing, a plurality of normal alignment regions 130 is obtained. The normal alignment regions 130 mainly are formed at a windward side 102a of the scan line 102, a windward side 106a of the storage electrode line 106, a windward side 104a of the data line 104, and a windward side 110a of the switch device 110. However, since the scan lines 102, the data lines 104, the storage electrode lines 106, and the switch devices 110 are protruded from the surface of the substrate 101, abnormal alignment regions 140 are formed at a leeward side 102b of the scan line 102, a leeward side 104b of the data line 104, a leeward side 106b of the storage electrode line 106 and a leeward side 110b of the switch device 110. In the abnormal alignment regions 140, the microgrooves that provide anchoring energy are not formed. As shown in FIG. 1, the abnormal alignment regions 140 are formed at where perpendicular to the first component direction 120a of the alignment direction 120, specifically, at the leeward side 104b of the data line 104 and the leeward side 110b of the switch devices 110. In the same concept, the abnormal alignment regions 140 are formed at where perpendicular to the second component direction 120b of the alignment direction 120, specifically, at the leeward side 102b of the scan line 102 and the leeward side 106b of the storage electrode line 106. Briefly speaking, when rubbing the alignment material layer, the abnormal alignment regions 140 are always formed on the TFT array substrate 100 at the leeward sides 102b/104b/106b/110b of the elements corresponding to the alignment direction 120.
As mentioned above, since the microgrooves that provide anchoring energy are not formed in the abnormal alignment regions 140, the LC molecules cannot be oriented to the predetermined direction, and thus the LC molecules are disarranged in the abnormal alignment regions 140. Consequently, dark regions are observed in the abnormal alignment regions 140 when the LCD is turned on while light leakage is observed in the abnormal alignment regions 140 when the LCD is turned off. Furthermore, the disarranged LC molecules in the abnormal alignment regions 140 render adverse impact to the rotation of the LC molecules in the normal alignment regions 130, and thus the response time of the LCD panel is prolonged and the performance of the LCD is deteriorated. As a countermeasure against to the problem, the prior art developed to position the black matrix corresponding to the abnormal alignment regions 140. However, this approach suffers lowered aperture ratio.